Aerosol generators for generating an aerosol for inhalation are for example used for delivery of a drug substance to a human lung.
An aerosol generator for generating an aerosol comprises a casing in which an inhalation duct is provided. A nozzle is provided in the inhalation duct to spray a quantity of the inhalation liquid into the inhalation duct. In the inhalation duct, the inhalation liquid mixes with air or with another gas or gas mixture provided in the inhalation duct so as to form an aerosol, the aerosol then leaves the aerosol generator at an exit opening for inhalation by the user, such as a patient.
WO2008/138936 describes a metered dose liquid inhaler device.
In devices for generating a liquid inhalation aerosol, several factors may play a role.
Firstly, the drug substance is to be distributed into liquid droplets having a inhalable size and small size distribution, in order to allow the droplets to propagate into the lungs of a user effectively. In general, small size distributions enable lung targeting and a more effective propagation and deposition into the deeper lung regions of a user.
Secondly, deposition of the drug substance in the upper respiratory tract (especially mouth and throat) is to be minimized, as such deposition may not be effectively absorbed.
Thirdly, retention of the drug substance in the inhalation device itself is to be limited, so as to minimize losses and prevent contamination of the inhalation device.
Fourthly, variations in particle size distribution and aerosol dose emitting the inhalation device (drug administered to the user) is required to be minimized, so as to obtain a reliable administration of the drug substance to the user. Many factors may have an effect on the dose administered to the user, such as but not being limited to: variations in droplet size, variations in deposition in the inhalation device (retention losses), variations in deposition in the mouth and throat region, variations in inhalation air speed or variations in the dosage of drug substance per administration, etcetera.
All in all, despite many efforts, existing liquid inhaler devices appear to still provide a very wide range in the amount of drug substance that is effectively administered to the various regions of the lung, limiting a therapeutic index of drugs and their therapies.